#include<stdio.h>
int main()
{
	freopen("trapez.in","r",stdin);
	freopen("trapez.out","w",stdout);
int n,x,y,k,i,j,oriz[1001],vert[1001],o=1,s=0,nr=0;
double v[1001],aux;
scanf("%d",&n);
for(k=1;k<=n;k++){
        scanf("%d%d",&x,&y);
        oriz[o]=x;
        vert[o]=y;
        o++;
	}
	
k=1;
for(i=1;i<n;i++){
	for(j=i+1;j<=n;j++){
	v[k]=(vert[j]-vert[i])/(oriz[j]-oriz[i]);
	k++;
}
}
s=0;
	while(s==0){
		s=1;
		for(i=1;i<n;i++){
			for(j=i+1;j<=n;j++){
				if(v[i]>v[j]){
					aux=v[i];
					v[i]=v[j];
					v[j]=aux;
					s=0;
				}
			}
		}
	}
for(i=1;i<n;i++){
	for(j=i+1;j<=n;j++){
		if(v[i]==v[j]){
			nr++;
		}
	}
}
printf("%d",nr);
return 0;
}